function y = e_t2(x)
%Extended Tridiagonal-2 Function   
%x0= [1.,1.,...,1.]..  
%fmin=n/2
%Author:shi yangyang
n=length(x);
y=ones(1,n-1);
c=0.1;
for i=1:1:n-1
    y(i)=(x(i)*x(i+1)-1.d0)^2 +c*(x(i)+1.0)*(x(i+1)+1.0);
end
y=sum(y);